This invention relates generally to piano construction and more particularly to a novel and improved soundboard for a piano.
Pianos have traditionally been built with soundboards constructed entirely of wood. It is known that relatively closely grained spruce wood produces superior soundboards. Additionally, it has been the practice to quarter-saw spruce boards for piano soundboards. Consequently, a board sawn in this fashion can be no wider than the radius of the log from which it is sawn. Moreover, since the center and sap wood are to be avoided, the width of such boards is further limited. Thus, it has been conventional practice to use a number of spruce boards of an appropriate thickness and edge-joined, as by gluing, to make up the necessary width of a soundboard.
Additionally, it has been found that for best sound propagation in a soundboard the elasticity should be high and density low. Thus, many spruce or pine woods are not satisfactory since their growth is generally too fast, leaving too open a grain, which results in inappropriate density and elasticity. Consequently, only selected spruce woods are suitable for construction of a piano soundboard and these are generally grown under somewhat adverse climatic conditions, whereby the growth is slow and the grain rather closely spaced. In this regard, it has been found that the preferred grain spacing is on the order of ten annular rings per inch, from which it can be seen that only relatively old trees are suitable for obtaining such boards.
As a result of all of the foregoing strictures, the supply of suitable spruce wood for piano soundboards is quite limited, and the production of such boards has become increasingly expensive.
In order to remedy this situation, some effort has been made in the past to construct laminated soundboards, formed from a number of relatively thin plies of wood.
In this latter regard, our copending application Ser. No. 969,722, filed Dec. 15, 1978, reveals one such laminated soundboard. As disclosed in our aforesaid application, we have discovered that it is advantageous to construct a three-ply soundboard wherein the top and bottom plies are of substantially equal thickness and wherein the center ply is of greater thickness than the sum of the thicknesses of these outer plies. Additionally, the grains of the outer plies are aligned in parallel with one another while the grain of the center or core ply is aligned at right angles to the grains of the two outer plies.
While the foregoing presents a superior soundboard structure, there is room for yet further improvement. Specifically, some desirable features have also been found to be provided by crowned or arched soundboards, whereby the prior art has endeavored in some cases to construct such soundboards. In this regard, it has been the practice to provide a press or molding device in the construction of a soundboard so as to impart the desired arch, crown or curvature thereto. However, many of these prior art methods of construction of such curved or arched soundboards have proven difficult and expensive and often fail to provide a sonically satisfactory soundboard which is reliable in service.
We have now discovered a soundboard construction which provides a natural arch or curvature in a three-ply laminated soundboard of the type shown in our copending application, mentioned above.